1. Field of the Invention
The present invention relates to a display panel and manufacturing method thereof. More particularly, the present invention relates to a high reliability liquid crystal display panel and manufacturing method thereof.
2. Description of Related Art
With the rapid development of multi-media systems, image data is mostly transmitted in a digital format through a network rather than in an analogue format through a cable. To match the life style of modern people, lighter and compact video or image display devices are also being designed. Although the conventional cathode ray tube (CRT) has high display quality and relatively low production cost, the electron gun inside the CRT not only produces hazardous radiation but also renders it bulky.
With recent advance in opto-electronic fabricating techniques and the maturity of semiconductor manufacturing processes, the development of flat panel display devices has to proceed quite rapidly. In particular, liquid crystal displays (LCD) have gradually replaced the conventional CRT and have become the mainstream display product due to its low operating voltage, radiation-free illumination, lightness and small volume occupancy.
A liquid crystal display (LCD) mainly comprises a liquid crystal display panel and a back light module. The liquid crystal display panel further comprises a color filter substrate, an active device array substrate and a liquid crystal layer sandwiched between the two substrates. The back light module provides a surface light source necessary for the liquid crystal display panel for displaying images. To maintain a fixed distance of separation between the color filter substrate and the active device array substrate after assembling the liquid crystal display panel, a plurality of spacers are often disposed between the color filter substrate and the active device array substrate.
FIG. 1 is a schematic cross-sectional view of the structure of a conventional liquid crystal display panel. As shown in FIG. 1, the liquid crystal display panel 100 mainly comprises a color filter substrate 110, a thin film transistor array substrate 120, a liquid crystal layer 130, a sealant 140 and a plurality of spacers 150. The sealant 140 is located on the periphery of the color filter substrate 100 and the thin film transistor array substrate 120 and connected the color filter substrate 100 and the thin film transistor array substrate 120 together. The liquid crystal layer 130 completely fills the space bounded by the color filter substrate 110, the thin film transistor array substrate 120 and the sealant 140. In addition, the spacers 150 are ball spacers disposed between the color filter substrate 110 and the thin film transistor array substrate 120 so that the two substrates are set at a fixed distance apart. However, these ball spacers 150 within the liquid crystal display panel tend to gather in one place when the liquid crystal display panel is shaked. Therefore, the twisting of the liquid crystal molecules near the collection of ball spacers 150 is reduced in the presence of an electric field in the usual manner leading to the so-called ‘spacer leakage’.
To reduce the aforementioned problem, a spacer on color filter (SOC) technique has been developed. In this technique, a plurality of spacers made from an organic photosensitive material is formed on the black matrix of a color filter substrate. Therefore, after joining the color filter substrate and the thin film transistor array substrate, the spacers will be disposed on top of the scan line, common line or data line of the thin film transistor array substrate.
It should be noted that the size and function of a liquid crystal display panel continues to expand because this is the trend. For example, liquid crystal televisions having an associated speaker or other wide display devices are quite common. Because of the weight of a large substrate and the acoustic vibration produced by the speaker, the color filter substrate and the thin film transistor array substrate may separate from each other once the sealant reaches an aging or fatigue limit or the spacers are uneven. This often leads to an abnormal display or a premature failure. Although the problem can be ameliorated by increasing the width of the sealant so that the upper and lower substrate are more firmly sealed together, the additional width in the sealant often inconveniences production (coating and hardening) and panel edge narrowing.
In view of the problems, methods of improving the reliability and increasing the size of a liquid crystal display panel are critical for expanding the market share in display products.